U.S. patent application number 13/867876 was filed with the patent office on 2014-03-06 for semiconductor structure.
This patent application is currently assigned to CHIPMOS TECHNOLOGIES INC.. The applicant listed for this patent is CHIPMOS TECHNOLOGIES INC.. Invention is credited to TSUNG JEN LIAO.
Application Number | 20140061906 13/867876 |
Document ID | / |
Family ID | 50186345 |
Filed Date | 2014-03-06 |
United States Patent
Application |
20140061906 |
Kind Code |
A1 |
LIAO; TSUNG JEN |
March 6, 2014 |
SEMICONDUCTOR STRUCTURE
Abstract
A semiconductor structure includes a semiconductor substrate, a
metal layer formed on the semiconductor substrate, a conductive
pillar, and a solder ball. The conductive pillar is formed on and
electrically connected with the metal layer, wherein the conductive
pillar has a bearing surface and a horizontal sectional surface
under the bearing surface, and the contact surface area of the
bearing surface is larger than the area of the horizontal sectional
surface. The solder ball is located on the conductive pillar and
covers the bearing surface.
Inventors: |
LIAO; TSUNG JEN; (HSINCHU,
TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CHIPMOS TECHNOLOGIES INC. |
Hsinchu |
|
TW |
|
|
Assignee: |
CHIPMOS TECHNOLOGIES INC.
Hsinchu
TW
|
Family ID: |
50186345 |
Appl. No.: |
13/867876 |
Filed: |
April 22, 2013 |
Current U.S.
Class: |
257/738 |
Current CPC
Class: |
H01L 2224/1132 20130101;
H01L 2224/11334 20130101; H01L 24/11 20130101; H01L 2924/00014
20130101; H01L 2224/131 20130101; H01L 2224/13018 20130101; H01L
2224/1147 20130101; H01L 2224/1183 20130101; H01L 2924/00014
20130101; H01L 2924/12042 20130101; H01L 24/05 20130101; H01L
2224/05027 20130101; H01L 2224/11462 20130101; H01L 2224/13005
20130101; H01L 2224/05572 20130101; H01L 2224/11462 20130101; H01L
2224/05572 20130101; H01L 2224/05024 20130101; H01L 2224/05027
20130101; H01L 2924/014 20130101; H01L 2924/206 20130101; H01L
2924/00014 20130101; H01L 2924/00014 20130101; H01L 2224/05099
20130101; H01L 2924/00014 20130101; H01L 2224/05552 20130101; H01L
2924/00 20130101; H01L 2924/00012 20130101; H01L 2924/00014
20130101; H01L 2924/00014 20130101; H01L 2224/11903 20130101; H01L
2224/0401 20130101; H01L 2224/11334 20130101; H01L 2224/13076
20130101; H01L 2924/12042 20130101; H01L 2224/1132 20130101; H01L
2924/00012 20130101; H01L 2224/11831 20130101; H01L 2224/13018
20130101; H01L 2224/131 20130101; H01L 2224/13082 20130101; H01L
24/13 20130101; H01L 2224/11849 20130101; H01L 2224/13005 20130101;
H01L 2224/1183 20130101; H01L 2924/00014 20130101 |
Class at
Publication: |
257/738 |
International
Class: |
H01L 23/00 20060101
H01L023/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 31, 2012 |
TW |
101131682 |
Claims
1. A semiconductor structure comprising: a semiconductor substrate;
a metal layer formed on the semiconductor substrate; a conductive
pillar formed on the metal layer and electrically coupled with the
metal layer, wherein the conductive pillar comprises a bearing
surface and a horizontal cross-sectional surface under the bearing
surface, and the contact surface area of the bearing surface is
larger than the area of the horizontal cross-sectional surface; and
a solder ball placed on the conductive pillar and covering the
bearing surface.
2. The semiconductor structure according to claim 1, wherein the
contact surface area of the bearing surface is larger than or equal
to 1.2 times the area of the horizontal cross-sectional
surface.
3. The semiconductor structure according to claim 2, wherein the
semiconductor structure comprises a pillar height measured from the
highest point of the bearing surface to a surface of the metal
layer and a lowest point height measured from the lowest point of
the bearing surface to the surface of the metal layer, wherein the
lowest point height is between 70% and 95% of the pillar
height.
4. The semiconductor structure according to claim 3, wherein the
bearing surface is a concave surface.
5. The semiconductor structure according to claim 3, wherein the
bearing surface comprises at least one protrusion.
6. The semiconductor structure according to claim 5, wherein the
bearing surface further comprises a first plane surrounding the
protrusion, and the protrusion comprises a sidewall, wherein the
angle included by the sidewall and the first plane is between 70
and 90 degrees.
7. The semiconductor structure according to claim 3, wherein the
bearing surface comprises a wall and a concave region, and the wall
surrounds the concave region.
8. The semiconductor structure according to claim 7, wherein the
wall comprises an inner sidewall, and the angle included by the
inner sidewall and a surface of the concave region is between 70
and 90 degrees.
9. The semiconductor structure according to claim 2, wherein the
conductive pillar comprises a pillar height measured from the
highest point of the bearing surface to a surface of the metal
layer, and a distance between the highest point of the bearing
surface to the lowest point of the bearing surface is between 5%
and 15% of the pillar height.
10. The semiconductor structure according to claim 9, wherein the
bearing surface is a concave surface.
11. The semiconductor structure according to claim 9, wherein the
bearing surface comprises at least one protrusion.
12. The semiconductor structure according to claim 11, wherein the
bearing surface further comprises a first plane surrounding the
protrusion, and the protrusion comprises a sidewall, wherein the
angle included by the sidewall and the first plane is between 70
and 90 degrees.
13. The semiconductor structure according to claim 9, wherein the
bearing surface comprises a wall and a concave region, and the wall
surrounds the concave region.
14. The semiconductor structure according to claim 13, wherein the
wall comprises an inner sidewall, and the angle included by the
inner sidewall and a surface of the concave region is between 70
and 90 degrees.
15. The semiconductor structure according to claim 1, wherein the
metal layer is an under bump metallization (UBM).
Description
BACKGROUND
[0001] 1. Technical Field
[0002] The present invention generally relates to a semiconductor
structure, and more particularly, the improvement of the
bondability between a solder ball and an element it adheres to.
[0003] 2. Related Art
[0004] As semiconductor technology changes, the electronic
engineering goes from thick film to thin film and to a more
minimized scale of the devices. Semiconductor packaging itself is a
process of making connection between different devices to form
electrical circuits; therefore, to keep up with the rapidly changed
semiconductor technology, packaging technique must also
advance.
[0005] In semiconductor packaging, the connection between solder
balls and chips or other components needs to meet certain
reliability to avoid electrical malfunction or breakdown after
packaging. In most situations, solder balls are adhered to the bond
pads or conductive pillars on a chip. However, practically, peeling
off or ineffective adherence of the solder balls is likely to
occur, leading to a reduction in production yield.
[0006] Therefore, a method to increase the bondability between
solder balls and chips so as to ensure the reliability is described
in further detail.
SUMMARY
[0007] In one embodiment of the present invention, a semiconductor
structure includes a semiconductor substrate; a metal layer formed
on the semiconductor substrate; a conductive pillar formed on the
metal layer and electrically coupled with the metal layer. The
conductive pillar includes a bearing surface and a horizontal
cross-sectional surface under the bearing surface. A solder ball is
placed on the conductive pillar. The contact surface area of the
bearing surface is larger than the area of the horizontal
cross-sectional surface.
[0008] In one embodiment of the present invention, the bearing
surface is not a horizontal plane and includes a protrusion located
in the center.
[0009] In one embodiment of the present invention, the bearing
surface is not a horizontal plane but a concave surface.
[0010] In one embodiment of the present invention, the bearing
surface is not a horizontal plane and includes a wall and a concave
region, wherein the wall surrounds the concave region.
[0011] In one embodiment of the present invention, the metal layer
is an under bump metallization (UBM).
[0012] To provide a better understanding of the characteristics and
advantages of the present invention, a detailed explanation is
provided in the following embodiments with reference to the
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The invention will be described according to the appended
drawings in which:
[0014] FIGS. 1A and 1B show a semiconductor structure with a
bearing surface of the conductive pillar comprising a protrusion
according to one embodiment of the present invention;
[0015] FIGS. 2A-2D show the manufacturing processes of fabricating
a semiconductor structure with a bearing surface of the conductive
pillar comprising a protrusion according to one embodiment of the
present invention;
[0016] FIG. 3 shows a semiconductor structure with a bearing
surface of the conductive pillar comprising a protrusion according
to one embodiment of the present invention;
[0017] FIG. 4 shows a semiconductor structure with a concave
bearing surface of the conductive pillar according to one
embodiment of the present invention;
[0018] FIG. 5 shows a semiconductor structure with a bearing
surface of the conductive pillar comprising a concave region
according to one embodiment of the present invention;
[0019] FIG. 6 shows a semiconductor structure with a bearing
surface of the conductive pillar comprising a plurality of
protrusions according to one embodiment of the present invention;
and
[0020] FIGS. 7 and 8 show the semiconductor structures having
solder balls placed on the bearing surfaces of the conductive
pillars according to the embodiments of the present invention.
DESCRIPTION OF THE EMBODIMENTS
[0021] The following detailed description states the instructions
or methods of the present invention. The detailed descriptions
should not limit the present invention. It should also be realized
that any equivalent functions or devices do not depart from the
spirit and scope of the invention as set forth in the appended
claims.
[0022] FIG. 1 is an embodiment of the present invention, showing a
semiconductor structure 10. The semiconductor structure 10 includes
a semiconductor substrate 100, which may be a semiconductor wafer
or a chip. The semiconductor structure 10 also includes a metal
layer 101 formed on the semiconductor substrate 100, where the
metal layer 101 may be a bond pad 106 of a semiconductor wafer or a
chip, an under bump metallization (UBM), a redistribution layer
(RDL), or a layer including a bond pad 106, an UBM 105 and a RDL
102 as shown in FIG. 1B. In this description, they are generally
called metal layers, and the main function of the metal layers is
to provide the route for electrical currents. A conductive pillar
200 is formed on the metal layer 101 and coupled with the metal
layer 101. The conductive pillar 200 has a bearing surface 210 for
other elements such as a solder ball 300 to be adhered thereon as
shown in FIG. 1A. In this embodiment, the bearing surface 210 is
not a horizontal plane, as shown in FIG. 1, wherein a protrusion
240 lies in the center of the plane. The total surface area or
so-called the contact surface area is the sum of the surfaces
210a.about.210e. A horizontal cross-sectional surface 220 of the
conductive pillar 200 is further defined herein as being under the
bearing surface 210. As shown in FIG. 1A the horizontal
cross-sectional surface 220 is a cross-section taken along line
AA'. Since the contact surface area of the bearing surface 210 is
larger than the area of the horizontal cross-sectional surface 220,
thus the increased contact area between the solder ball 300 and the
conductive pillar 200 can improve the adherence in comparison with
a horizontal bearing surface. After applying a thermal process such
as reflow or laser heating, the solder ball 300 then covers the
bearing surface 200 of the conductive pillar 200. The method of
placing the solder ball 300 on the conductive pillar 200 may be
selected from but not limited to screen printing, vapor deposition,
electroplating, ball drop, or ball spray.
[0023] FIGS. 2A-2D show a process of fabricating the semiconductor
structure 10. First, a semiconductor substrate 100 is provided,
wherein the semiconductor substrate 100 includes the metal layer
101. Then, as shown in FIG. 2B, a patterned mask 500 is formed of a
insulating material such as photoresist or dry film on the
semiconductor substrate 100, and a conductive pillar 200 is then
formed on the metal layer 101 by electroplating, for example,
according to the patterned mask 500. The material of the conductive
pillar 200 may be any kind of conductive material, for instance, a
copper pillar in the present embodiment. FIG. 2C depicts the step
of coating a photoresist 400 on a predetermined region of the
bearing surface 200 of the conductive pillar 200, followed by
etching out the region uncovered by the photoresist 400 to a
thickness d as shown in FIG. 3. After the photoresist 400 is
removed, the bearing surface 210 having a protrusion 240, shown in
FIG. 2D, is formed. The total surface area of the bearing surface
210 with the protrusion 240 is larger than the surface area of a
horizontal plane.
[0024] In another embodiment of the present invention, after a
patterned mask 500 is formed on the semiconductor substrate 100 and
a conductive pillar 200 is formed on the metal layer 101 as shown
in FIG. 2B, a wet etching is directly applied on the bearing
surface 210 to form a concave surface. Once the patterned mask 500
is removed, the conductive pillar 200 with a concave bearing
surface 210 is then formed as shown in FIG. 4. Similarly, in
another embodiment of the present invention, after a patterned mask
500 is formed on the semiconductor substrate 100 and a conductive
pillar 200 is formed on the metal layer 101 as shown in FIG. 2B, a
laser carving is applied directly on the bearing surface 210 so
that after the patterned mask 500 is removed, the bearing surface
210 having a protrusion 240 as shown in FIG. 2D is then formed, or
the bearing surface 210 having a wall 218 and a concave region 216
as shown in FIG. 5 is then formed.
[0025] Moreover, during the process of forming the bearing surface
210, the total surface area of the bearing surface 210 may be
changed by the combination of etching and laser carving, as shown
in FIG. 6, so that a plurality of protrusions 240 or concave
regions 216 can be formed on the bearing surface 210. By this way,
the contact surface area of the bearing surface 210 can be adjusted
as per requirements. Other shapes of the bearing surface 210 could
also be achieved by the combination of dry etch, wet etch, and
laser etching processes.
[0026] In the present invention, the contact surface area of the
bearing surface 210 could be changed by a process adjustment. In
reference to FIG. 1A and FIG. 1B, in one embodiment, the contact
surface area of the bearing surface 210 is larger than or equal to
1.2 times the area of the horizontal cross-sectional surface 220.
In another embodiment, the contact surface area of the bearing
surface 210 is between 1.2 and 1.6 times larger than the area of
the horizontal cross-sectional surface 220. In another embodiment,
the contact surface area of the bearing surface 210 is between 1.2
and 2 times larger than the area of the horizontal cross-sectional
surface 220. In another embodiment, the contact surface area of the
bearing surface 210 is between 1.5 and 2 times larger than the area
of the horizontal cross-sectional surface 220. In another
embodiment, the contact surface area of the bearing surface 210 is
between 1.5 and 2.5 times larger than the area of the horizontal
cross-sectional surface 220. In another embodiment, the contact
surface area of the bearing surface 210 is between 1.5 and 3 times
larger than the area of the horizontal cross-sectional surface 220.
In another embodiment, the contact surface area of the bearing
surface 210 is between 2 and 2.5 times larger than the area of the
horizontal cross-sectional surface 220. In yet another embodiment,
the contact surface area of the bearing surface 210 is between 2
and 3 times larger than the area of the horizontal cross-sectional
surface 220.
[0027] According to an embodiment of the present invention, shown
in FIG. 3, the semiconductor structure 10 has a pillar height H1
measured from the highest point of the bearing surface 210 to the
surface of the metal layer 101 and a lowest point height h measured
from the lowest point of the bearing surface 210 to the surface of
the metal layer 101, wherein the lowest point height h is between
70% and 95% of the pillar height H1. In another embodiment, the
lowest point height h is between 65% and 95% of the pillar height
H1. In another embodiment, the lowest point height h is between 80%
and 95% of the pillar height H1. In another embodiment, the lowest
point height h is between 85% and 95% of the pillar height H1. In
yet another embodiment, the lowest point height h is between 70%
and 85% of the pillar height H1.
[0028] Referring to FIG. 3 and FIG. 4, the conductive pillar 200
includes a pillar height H1 or H2 measured from the highest point
of the bearing surface 210 to the surface of the metal layer 101,
and a distance d between the highest point of the bearing surface
210 to the lowest point of the bearing surface 210 is between 5%
and 15% of the pillar height H1 or H2. In another embodiment, the
distance d is between 5% and 7% of the pillar height H1 or H2. In
another embodiment, the distance d is between 7% and 10% of the
pillar height H1 or H2. In another embodiment, the distance d is
between 10% and 13% of the pillar height H1 or H2. In another
embodiment, the distance d is between 13% and 15% of the pillar
height H1 or H2. In yet another embodiment, the distance d is
between 8% and 13% of the pillar height H1 or H2.
[0029] Referring to FIG. 3, the bearing surface 210 includes a
first plane 212 surrounding the protrusion 240, and the protrusion
240 includes a sidewall 214, wherein the angle included by the
sidewall 214 and the first plane 212 is between 70 and 90
degrees.
[0030] Referring to FIG. 5, the wall 218 includes an inner sidewall
219, and the angle included by the inner sidewall 219 and a surface
of the concave region 216 is between 70 and 90 degrees.
[0031] FIGS. 7 and 8 show an embodiment in which the solder ball
300 is placed on the bearing surface 210. In any embodiment of the
present invention, a larger contact area between the solder ball
300 and the bearing surface 210 of the conductive pillar 200 may be
obtained; hence, the bondability between the solder ball 300 and
the conductive pillar 200 can be enhanced as well as the
reliability of the semiconductor structure.
[0032] Although the technique content and characteristics of the
invention have been described herein, many modifications and
addictions may be made by those skilled in the relevant art within
the scope of the invention. Therefore, it will be apparent that the
invention is not limited thereto, and many modifications and
addictions will be covered by the following claims.
* * * * *